Transit mode share, in fact, is where density is least relevant. This may seem surprising, but only if you believe that density is the only way to control the relative value that people get from various modes. The transit boosters who worry about density actually believe that it's possible in the short term to increase the value of transit by throwing more money at it, but that that's unsustainable in the long run. Their big blind spot is that we actually have quite a bit of control over the value of driving, if we can find the political will.

1. Give transit its own right-of-way and good terminals
2. Make it hard to use cars
3. Make it expensive to use cars
4. Profit!

Many transit advocates have enough exposure to the concept of (3) in the form of congestion pricing and gasoline prices, but they seem very resistant to considering step (2), probably because they don't want to be accused of wanting to take anyone's car away. The Very Serious People are all afraid to talk about decreasing the size of the road network.

But what if, while Spain was building all those high-speed rail lines, they didn't also pump billions into a truly gigantic highway network? If drivers faced constant congestion on old highways, wouldn't we expect higher ridership on the trains? Wouldn't we also expect that if the highway network was old and small enough, but the train network was the size it is today, eventually there would be enough demand for the trains that they would be completely profitable - operations and capital?

You can do the same thought experiment with any place. No matter how sparsely populated it is, just subtract some roads while keeping the rail and/or bus network constant, and eventually the place "supports transit." Take Wyoming. Now imagine it without interstate highways. Would that be enough to support restored passenger service on the train lines? How about if we turn all the roads to gravel?

Back in 2010, I had a similar discussion on Human Transit about the supposed convenience of cars. A lot of people had problems with the idea that convenience was dependent on the quality of the infrastructure, but I think I showed that if you throw enough money at any transportation system you can make it feel convenient to its users.

Similarly, if you make the car infrastructure shitty enough and expensive enough, you can make transit feel like a bargain. Density may make it politically easier to support transit expansion or harder to support road expansion, but that's not a matter of "the density to support transit," it's "the density to make it likely enough that transit will receive more political support than roads," which is not the same thing at all.

If you're really not convinced, I challenge you to come up with a place, or a route, where you can't increase transit ridership by taking away roads or increasing prices. If you want data, I have density and mode share figures for all of the municipalities and census-designated places in the New York Combined Statistical Area. Go for it.

Fort McMurray, Alberta: Attempts to worsen the road infrastructure in the area would likely encourage the oil companies to leave.

If the companies leave, people would leave and transit ridership would be lower when there are fewer people left to take it.

The companies would likely move to places where they can increase efficiency, reduce carnage (are the roads allowed to deteriorate and become unsafe in your scenario?), and avoid political environments that utterly ignore economics.

Agree in a narrow sense. It is always possible to reduce car use and increase transit use by reducing auto infrastructure and increasing transit infrastructure (so long as the net transportation cost is low enough that people don't move out entirely).

In a more general sense, I suspect there is a density below which it is more cost-efficient to provide auto infrastructure than transit infrastructure. I expect it lies well below where it is commonly assumed to be in the US, for all the reason you commonly cite against car travel. It's probably infeasible to provide local bus service to rural Montana, but replacing interstate with regional train service could still be effective.

Cap'n, I'll admit I may be taking your "challenge" too much at face value. I apologize if you think I'm attacking you personally. I'm not.

I'm trying to imagine "worse roads" scenarios that could lead to reduced transit ridership. To do that, I assumed a devil's advocate role and I took the perspective of interests in the oil industry. The pejorative "social engineering" was from their perspective, not mine. In the future, I'll avoid overly pithy posts that may be misunderstood.

If you take a place like Wyoming and strip it of roads, then people will just not have transportation. Not every place can support trains, and that's not just a mode share question. Transit works best along high-intensity linear corridors.

I'm going to come in on Alon's side. There are particular, very rural places that are so low-density that they will likely continue to require some form of personal transportation. These are the places where the horse once ruled, and now the truck does.

In the town I went to high school in (Phelan, CA), the minimum lot size is 2.5 acres. There are 14,000 people there, sprawled out across 61 square miles. Most of the roads are dirt. Believe it or not, there is transit there- the Victor Valley Transit Authority runs a bus along the main highway at 90 minute headways. Most of the roads are dirt, and many people live far outside of walking distance of the paved roads.

I don't think there's a way to make transit work there, and the roads really can't get much worse. If gas were suddenly $10 or $20 a gallon, or if the highway were to become tolled, transit ridership would probably increase, but that's such a minimal standard. It still probably wouldn't increase to a self-sustaining level. Most people would likely switch to either mountain bikes or horses.

Part of the Capn's argument is that people who were suddenly deprived of convenient automobile transit, whether because the roads were all repaved with gravel or because motor vehicle fuel became prohibitively expensive, would move to town centers where they could get a bus to work and do their errands on foot or bike.

In such a case, the Phelan CA town council would quickly adjust the zoning and make it possible for families to live closer together. Just my opinion.

If roads get bad enough in Fort McMurray, the oil companies that actually use them for moving their equipment around will have to start paying to maintain them, or else just pay to extend rail branches to their oilfields and switch to rail. For passenger transport, the city itself is sufficiently compact that it can be served very effectively by a few bus routes, and that would be a pretty decent way of getting people to work. For examples of how this works out in practice, see industrial towns in the former Soviet Union.

Jonathan, you're missing two things. First, the scenario you're hypothesizing is not one in which transit use is high at low density, but one in which density rises. Second, rail ridership in small towns was not high before zoning. Small towns outside major metro areas were the first to lose even their regional rail connections, which were the only transit they had, often before zoning, sometimes even before cars were widespread.

And trying to do a zero-car thought experiment really is beside the point. Think not about zero cars; think about 100 cars per 1,000 people instead. In such a scenario, a large majority of travel in major metro areas is on transit (larger in the city than in the suburbs), and a large majority of travel in rural areas isn't.

Fort McMurray Alberta:The oil companies are there because the resources are there, road costs would have to be extremely high to make anyone leave.There are traffic jams on the highway that las for hours, and there is a fairly sucessful local transit system. There are also hige numbers of private busses that run direct to the indvidual work site, the big oisands plants and construction sites. Due to regulations that new developments must not increase traffic on the highway, major projects include camps for employees, some housing as many as 5,000 workers who all pile onto buses every morning, because there is no parking available at the plants or at the camps.

When the 2 weeks work is done, they all pile onto the bus back to edmonton, or onto a planeright at the plant site, and direct to cities all over the country.

It works because the price of driving is high, and the "public transit" is is included in the union contract. And because hthere is only one road from the plants into town, and only one road out to the rest of the world.